Image stabilization apparatus, image stabilization control method, and computer-readable storage medium

ABSTRACT

An image stabilization apparatus comprises: a first obtaining unit that obtains orientation information of an image capturing apparatus; a determining unit that, on the basis of the orientation information, determines a reference position of an image sensor included in the image capturing apparatus; and a calculating unit that calculates a correction amount for performing image stabilization by moving a position of the image sensor from the reference position in a plane intersecting with an optical axis. The reference position is different between when the orientation information indicates that the image capturing apparatus is in a first orientation and when the orientation information indicates that the image capturing apparatus is in a second orientation.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 16/867,595,filed May 6, 2020, the entire disclosure of which is hereby incorporatedby reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an image stabilization apparatus, animage stabilization control method, and a computer-readable storagemedium.

Description of the Related Art

Some image capturing apparatuses have image stabilization mechanisms forsuppressing image blur caused by the photographer's hand shaking or thelike. An image stabilization mechanism corrects image blur by moving animage sensor in orthogonal and rotational directions relative to anoptical axis. When there is a high amplitude of vibration, the imagesensor is moved extensively to suppress the resulting image blur.However, when there is no leeway in terms of the size of the imagecircle of the lens attached to the image capturing apparatus, or whenmanufacturing error or the like has resulted in the center of the imagecircle being shifted, moving the image sensor extensively makes itimpossible to obtain a sufficient amount of light at the corner parts ofthe image sensor. This results in vignetting, where the corner parts ofthe shot image are dark. If the image sensor is therefore moved within arange where such vignetting has little effect, the amount of movement ofthe image sensor will not be sufficient to fully correct the image blur.

Accordingly, Japanese Patent Laid-Open No. 9-027926 proposescommunicating position information of the center of the image circle ofa lens (i.e., the optical axis of the lens) to the camera and thenshifting the image sensor so that the center of the image sensorcoincides with the optical axis of the lens. Doing so makes it possibleto eliminate shifting of the lens optical axis caused by manufacturingerror or the like, which in turn ensures, to a certain degree, therequired amount of movement in the image sensor for correcting imageblur.

However, the center position, size, and so on of the image circle differdepending on the orientation of the image capturing apparatus, as wellas the state of the lens, including the focal length, the focal state,the aperture, and so on. Thus in an interchangeable lens-type imagecapturing system, the lens which is attached and used may notnecessarily have optical axis position information that corresponds tothe orientation of the image capturing apparatus, the state of the lens,and so on. Accordingly, in situations where information of the imagecircle cannot be obtained, it has been unclear how to appropriatelydetermine a target position for the center of the image sensor at whichthere will be little loss of image quality when correcting image blur.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of the abovesituation, and makes it possible to correct image blur while suppressingthe effects of vignetting in response to a variety of situations in animage capturing system.

According to the present invention, provided is an image stabilizationapparatus, comprising: a first obtaining unit that obtains orientationinformation of an image capturing apparatus; a determining unit that, onthe basis of the orientation information, determines a referenceposition of an image sensor included in the image capturing apparatus;and a calculating unit that calculates a correction amount forperforming image stabilization by moving a position of the image sensorfrom the reference position in a plane intersecting with an opticalaxis, wherein the reference position is different between when theorientation information indicates that the image capturing apparatus isin a first orientation and when the orientation information indicatesthat the image capturing apparatus is in a second orientation, andwherein each unit is implemented by at least one processor or circuitry,or combination thereof.

Further, according to the present invention, provided is an imagestabilization apparatus, comprising: a first obtaining unit thatobtains, from at least one of an image capturing apparatus and a lensunit attached to the image capturing apparatus, a state of the imagecapturing apparatus and/or the lens unit; a second obtaining unit that,when the state satisfies a predetermined condition, obtains lensinformation corresponding to the state from lens information of the lensunit corresponding to a plurality of predetermined states; a determiningunit that determines a reference position of an image sensor included inthe image capturing apparatus; and a calculating unit that calculates acorrection amount for performing image stabilization by moving aposition of the image sensor from the reference position in a planeintersecting with an optical axis, wherein when the state satisfying thepredetermined condition is not obtained by the first obtaining unit, thedetermining unit determines the reference position through a firstmethod based on information aside from the lens information, and whereineach unit is implemented by at least one processor or circuitry, orcombination thereof.

Further, according to the present invention, provided is an imagestabilization control method, comprising: obtaining orientationinformation of an image capturing apparatus; determining, on the basisof the orientation information, a reference position of an image sensorincluded in the image capturing apparatus; and calculating a correctionamount for performing image stabilization by moving a position of theimage sensor from the reference position in a plane intersecting with anoptical axis, wherein the reference position is different between whenthe orientation information indicates that the image capturing apparatusis in a first orientation and when the orientation information indicatesthat the image capturing apparatus is in a second orientation.

Further, according to the present invention, provided is an imagestabilization control method, comprising: obtaining, from at least oneof an image capturing apparatus and a lens unit attached to the imagecapturing apparatus, a state of the image capturing apparatus and/or thelens unit; obtaining, when the state satisfies a predeterminedcondition, lens information corresponding to the state from lensinformation of the lens unit corresponding to a plurality ofpredetermined states; determining a reference position of an imagesensor included in the image capturing apparatus; and calculating acorrection amount for performing image stabilization by moving aposition of the image sensor from the reference position in a planeintersecting with an optical axis, wherein when the state satisfying thepredetermined condition is not obtained, in the determining, thereference position is determined through a first method based oninformation aside from the lens information.

Further, according to the present invention, provided is acomputer-readable storage medium in which is stored a program forcausing a computer to function as the respective units in the imagestabilization apparatus comprising: a first obtaining unit that obtainsorientation information of an image capturing apparatus; a determiningunit that, on the basis of the orientation information, determines areference position of an image sensor included in the image capturingapparatus; and a calculating unit that calculates a correction amountfor performing image stabilization by moving a position of the imagesensor from the reference position in a plane intersecting with anoptical axis, wherein the reference position is different between whenthe orientation information indicates that the image capturing apparatusis in a first orientation and when the orientation information indicatesthat the image capturing apparatus is in a second orientation.

Further, according to the present invention, provided is acomputer-readable storage medium in which is stored a program forcausing a computer to function as the respective units in the imagestabilization apparatus comprising: a first obtaining unit that obtains,from at least one of an image capturing apparatus and a lens unitattached to the image capturing apparatus, a state of the imagecapturing apparatus and/or the lens unit; a second obtaining unit that,when the state satisfies a predetermined condition, obtains lensinformation corresponding to the state from lens information of the lensunit corresponding to a plurality of predetermined states; a determiningunit that determines a reference position of an image sensor included inthe image capturing apparatus; and a calculating unit that calculates acorrection amount for performing image stabilization by moving aposition of the image sensor from the reference position in a planeintersecting with an optical axis, wherein when the state satisfying thepredetermined condition is not obtained by the first obtaining unit, thedetermining unit determines the reference position through a firstmethod based on information aside from the lens information.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments (with reference to theattached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the description, serve to explain the principles of theinvention.

FIG. 1 is a block diagram illustrating a functional configuration of animage capturing system according to embodiments of the presentinvention.

FIG. 2 is an exploded perspective view of an image sensor unit accordingto embodiments.

FIG. 3 is a flowchart illustrating operations of an image capturingapparatus according to embodiments.

FIG. 4A is a schematic diagram illustrating a relationship between animage circle of a lens and an image capturing region.

FIG. 4B is a diagram illustrating an example of an image captured whenshooting a solid surface having a uniform brightness after moving animage sensor to correct image blur in a situation as illustrated in FIG.4A.

FIG. 5 is a schematic diagram illustrating a relationship between animage circle of a lens and an image capturing region according toembodiments.

FIG. 6 is a schematic diagram illustrating a relationship between animage circle of a lens and an image capturing region according toembodiments.

FIG. 7 is a flowchart illustrating processing for moving the center ofan image sensor according to embodiments.

FIG. 8 is a flowchart illustrating operations in a first determinationmethod according to embodiments.

FIG. 9 is a flowchart illustrating operations in a second determinationmethod according to embodiments.

FIGS. 10A to 10C are diagrams illustrating examples of lens informationaccording to embodiments.

FIG. 11 is a flowchart illustrating operations of an image capturingapparatus according to a second embodiment.

FIG. 12 is a flowchart illustrating operations of an image capturingapparatus according to a third embodiment.

FIG. 13 is a flowchart illustrating processing for moving the center ofan image sensor according to a fourth embodiment.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments will be described in detail with reference tothe attached drawings. Note, the following embodiments are not intendedto limit the scope of the claimed invention. Multiple features aredescribed in the embodiments, but limitation is not made an inventionthat requires all such features, and multiple such features may becombined as appropriate. Furthermore, in the attached drawings, the samereference numerals are given to the same or similar configurations, andredundant description thereof is omitted.

FIG. 1 is a block diagram illustrating the functional configuration ofan image capturing system according to embodiments of the presentinvention. The image capturing system includes a camera body 100, whichis an image capturing apparatus, and a lens unit 200 which can beattached to and removed from the camera body 100.

First Embodiment

In the camera body 100, a microcomputer (“MPU” hereinafter) 101 is acontrol unit that comprehensively controls the operations of the variousconstituent elements of the image capturing system. The MPU 101 controlsa shutter driving circuit 104, an image signal processing circuit 105, aswitch sensor circuit 106, and an image stabilization driving circuit109. The MPU 101 also holds data in Electrically Erasable ProgrammableRead-Only Memory (EEPROM) 115. Furthermore, the MPU 101 loads data whichis temporarily needed in DRAM 116, and accesses that data whennecessary.

The MPU 101 communicates with a lens control circuit 202 within the lensunit 200 via a mount contact point 21. When the lens unit 200 is mountedto a mount part 120 of the camera body 100, the MPU 101 determineswhether or not it is possible to communicate with the lens controlcircuit 202 by receiving a signal through the mount contact point 21.Note that the mount part 120 is annular, and is configured so that thelens unit 200 can be mounted to and removed from the mount part 120.

The lens control circuit 202 controls the driving of a lens 201 and anaperture stop 205 in an imaging optical system via an autofocus (AF)driving circuit 203 and an aperture driving circuit 204, in response tocontrol signals received from the MPU 101. Although FIG. 1 illustratesonly a single lens 201 for the sake of simplicity, the lens 201 isactually constituted by multiple lenses, including a focus lens and thelike. Furthermore, the lens control circuit 202 reads out necessaryinformation by communicating with EEPROM 206 provided in the lens unit200. The EEPROM 206 stores lens information such as image circle centerposition information, image circle diameter information, information ofthe highest-resolution position, resolution distribution information,and the like for each individual lens unit 200.

The MPU 101 carries out focus detection computations according to aphase difference detection method on the basis of an image signalobtained by an image sensor 430 photoelectrically converting an opticalimage of a subject. Specifically, the MPU 101 calculates a defocusamount and direction using the image signal, and sends a control signalto the lens control circuit 202. The lens control circuit 202 carriesout control for moving the focus lens to an in-focus position via the AFdriving circuit 203 in accordance with the calculated defocus amount anddirection.

A shutter unit 32 is a mechanical focal plane shutter, and includesfront curtain blades and rear curtain blades. When not shooting, as wellas when shooting a moving image, the front curtain blades and the rearcurtain blades are held in an exposure position, which allows lightbeams to pass from the subject to the image sensor 430.

However, when shooting a still image, light beams for shooting an imageare allowed to pass by the front curtain blades performing exposuretravel, in which the front curtain blades move from a light-blockingposition to an exposure position. After a set exposure time (shutterspeed) has passed, the rear curtain blades perform light-blockingtravel, in which the rear curtain blades move from the exposure positionto the light-blocking position. This completes the shooting for a singleimage's worth of data. The shutter unit 32 is controlled by the shutterdriving circuit 104 in response to control commands from the MPU 101.Note that instead of front curtain blades, the exposure time may becontrolled by what is known as an “electronic front curtain”, whichresets charges in the image sensor 430.

An image sensor unit 400 includes an optical low-pass filter 410, theimage sensor 430, and an image stabilization mechanism unit. The imagesensor 430 is an image sensing device using a CMOS, a CCD, or the like,for example, and outputs an analog image signal by photoelectricallyconverting an optical image of a subject which has been formed. Althoughdetails will be given later, the image stabilization mechanism unitincludes a driving coil 460 and a position detection sensor 480. Imagestabilization operations are carried out by the image stabilizationdriving circuit 109 controlling the electrification of the driving coil460, and moving the image sensor 430, on the basis of the detectionsignal resulting from hand shake or the like.

The image signal processing circuit 105 carries out analog/digital (A/D)conversion processing on the analog image signal output from the imagesensor 430, and further executes image processing, such as noise removalprocessing, gain adjustment processing, and the like, on the obtaineddigital image data.

A color liquid crystal driving circuit 112 causes an image to bedisplayed in the screen of a color liquid crystal monitor 19, inaccordance with the image data output by the image signal processingcircuit 105. This makes it possible for a user to monitor the image heor she is about to shoot, confirm an image he or she has shot, and soon. The color liquid crystal driving circuit 112 also causes images tobe displayed in the screen of an eyepiece-based liquid crystal monitor30. The camera body 100 includes a viewfinder 33 through which thesubject can be observed, and the user can observe an image displayed inthe eyepiece-based liquid crystal monitor 30, in an optically-enlargedmanner, through an ocular lens 31 provided within the viewfinder 33.

The switch sensor circuit 106 detects a switch (SW) signal from anoperation member and outputs that signal to the MPU 101. FIG. 1illustrates a release switch (SW) 41 (41 a, 41 b), an imagestabilization setting switch (SW) 42, a power switch (SW) 43, and ashooting mode setting dial 44 as examples of operation members. Therelease SW 41 is a starting switch used when the user instructs shootingto start, and has a switch structure which is operated in steps. Forexample, a first switch SW1 (41 a) turns on with a first stroke, whenthe switch is pressed halfway or the like, and a second switch SW2 (41b) turns on with a second stroke, when the switch is fully depressed orthe like. The image stabilization setting SW 42 is a switch for settingimage stabilization processing on and off. The power SW 43 is a switchfor turning the power to the camera body 100 on and off. The shootingmode setting dial 44 is a rotational operation member used to select andset shooting modes such as still image shooting, moving image shooting,and the like.

A shake detection sensor 50 detects shake in the camera body 100 causedby the user's hand shaking, movement in the user's body, and so on. Anangular velocity sensor such as a gyrosensor or the like is used for theshake detection sensor 50. The shake detection sensor 50 detects, forexample, an angular velocity in each of a horizontal direction (an Xdirection) orthogonal to an image capturing optical axis, a verticaldirection (a Y direction) orthogonal to the image capturing opticalaxis, and a direction of rotation about the image capturing optical axis(a roll direction). A shake detection signal from the shake detectionsensor 50 is output to the MPU 101.

The position detection sensor 480 in the image sensor unit 400 includesa Hall device or the like, and detects a position of the image sensor430. The position detection sensor 480 detects displacement in the Xdirection, displacement in the Y direction, and rotational displacementin a direction about the optical axis (the roll direction), and outputsa position detection signal to the MPU 101.

An orientation detection sensor 60 detects an orientation of the camerabody 100. As the orientations of the camera, the orientation detectionsensor 60 detects an upright position, a vertical position rotated 90°to the right, a vertical position rotated 90° to the left, a state inwhich the lens is pointed downward, and a state in which the lens ispointed upward. The orientation detection sensor 60 furthermore detectsa pitched state (an intermediate state between the upright position anda state in which the lens is pointed downward or upward), a state ofrotation (an intermediate state between the upright position and thevertical position), and so on. An accelerometer is used for theorientation detection sensor 60, and an orientation detection signalexpressing the orientation detected by the orientation detection sensor60 is output to the MPU 101.

A proximity sensor 70 is disposed near a member that holds the ocularlens 31, and detects when the user's face is near the viewfinder 33. Inother words, the proximity sensor 70 detects whether or not the user islooking into the viewfinder of the camera body 100. An infrared lightprojecting/receiving sensor can be used for the proximity sensor 70. Anoutput signal from the proximity sensor 70 is output to the MPU 101.

The MPU 101 obtains a state of the lens unit 200 via the mount contactpoint 21 (here, the “state” refers to at least one of an F number, thefocal length, and the focal state), and also obtains an orientationsignal (orientation information) from the orientation detection sensor60. This information will be called the “state of the image capturingsystem” hereinafter.

The configuration of the image sensor unit 400 will be described nextwith reference to FIG. 2. FIG. 2 is an exploded perspective view of theimage sensor unit 400. The image capturing optical axis is defined as aZ axis, an axis in the horizontal direction orthogonal to the Z axis isdefined as an X axis, and an axis in the vertical direction orthogonalto both the Z axis and the X axis is defined as a Y axis. The positionalrelationships between the units will be described assuming that asubject side corresponds to a forward side. To correct image blur in theX direction, the Y direction, and the direction of rotation about theoptical axis (the roll direction), the image sensor unit 400 can movethe image sensor 430 in each of those directions. The optical low-passfilter 410 is a single birefringent plate, formed as a rectangle fromcrystal, and is disposed on the forward side of the image sensor 430.

A shift holder 420 is a mobile member that holds the optical low-passfilter 410 and the image sensor 430 and is capable of moving in the Xdirection, the Y direction, and the roll direction. The image sensor 430is fixed to the shift holder 420 by a fastening member (not shown), orwith an adhesive. A shift base 440 constitutes part of a base member ofthe image sensor unit 400, and is disposed on the rear side of the imagesensor 430. A front base 450 is a member which is substantially L-shapedwhen viewed from the front, and is disposed on the side of the shiftholder 420 opposite from the side on which the shift base 440 isdisposed (i.e., the forward side). The shift base 440 and the front base450 are formed from a soft magnetic material such as iron. Part of thefront base 450 is linked to the shift base 440, and is integrated withthe shift base 440. In other words, the shift base 440 and the frontbase 450 constitute the base member (fixing member) of the image sensorunit 400, and support the mobile member in a mobile state. The shiftbase 440 is fastened to a main part of the camera body 100.

As the driving coil 460 indicated in FIG. 1, an X direction driving coil460 a and Y direction driving coils 460 b and 460 c are provided. Thesecoils are soldered to a flexible board (not shown) and are affixed tothe shift holder 420 by an adhesive. The X direction driving coil 460 ais disposed on a right side of the image sensor 430 when viewed from thefront. The Y direction driving coils 460 b and 460 c are disposed on alower side of the image sensor 430, symmetrically with respect to a YZplane and with a predetermined gap between the coils in the X direction.Along with an X direction permanent magnet 470 a and Y directionpermanent magnets 470 b and 470 c, the X direction driving coil 460 aand the Y direction driving coils 460 b and 460 c constitute anelectromagnetic driving unit of the image sensor unit 400.

The X direction permanent magnet 470 a and the Y direction permanentmagnets 470 b and 470 c are affixed to the shift base 440 by anadhesive. The N pole and the S pole of the X direction permanent magnet470 a are arranged in the X direction, whereas the N pole and the S poleof the Y direction permanent magnets 470 b and 470 c are arranged in theY direction. The permanent magnets 470 a, 470 b, and 470 c are disposedopposing the driving coils 460 a, 460 b, and 460 c, respectively.Specifically, one side part of each driving coil always overlaps withthe N pole of the corresponding permanent magnet with respect to the Zdirection, and the other side of the driving coil always overlaps withthe S pole of the corresponding permanent magnet with respect to the Zdirection.

When the image stabilization driving circuit 109 electrifies the Xdirection driving coil 460 a, a magnetic flux produced by the drivingcoil 460 a and a magnetic flux produced by the X direction permanentmagnet 470 a interfere magnetically, which produces Lorentz force. Theshift holder 420 attempts to move linearly in the X direction relativeto the shift base 440, with the Lorentz force produced by theelectromagnetic driving unit acting as thrust (driving force).

On the other hand, when the image stabilization driving circuit 109electrifies the Y direction driving coils 460 b and 460 c, a magneticflux produced by the driving coils 460 b and 460 c and a magnetic fluxproduced by the Y direction permanent magnets 470 b and 470 c interferemagnetically, which produces Lorentz force. The shift holder 420attempts to move linearly in the Y direction relative to the shift base440, with the Lorentz force produced by the electromagnetic driving unitacting as thrust (driving force). Furthermore, the Y direction thrustsproduced in the driving coils 460 b and 460 c can be set to differentvalues by individually adjusting the magnitude of the currents in the Ydirection driving coils 460 b and 460 c. As a result, the shift holder420 can be rotated relative to the shift base 440.

A position detection sensor 480 a and position detection sensors 480 band 480 c are provided as the position detection sensor 480 illustratedin FIG. 1. The position detection sensor 480 a is a Hall device,disposed near the X direction driving coil 460 a, that detects Xdirection displacement of the mobile member, including the shift holder420. On the other hand, the position detection sensors 480 b and 480 care Hall devices, disposed near respective ones of the Y directiondriving coils 460 b and 460 c, that detect Y direction displacement ofthe mobile member, including the shift holder 420. Each of the positiondetection sensors 480 a, 480 b, and 480 c is disposed near themagnetization boundary of the corresponding opposing permanent magnet,is soldered to a flexible board or the like (not shown), and is affixedto the shift holder 420 by an adhesive. Each of the position detectionsensors 480 a, 480 b, and 480 c outputs an electrical signalcorresponding to a change in the magnetic flux produced from thecorresponding opposing permanent magnet.

A plurality of balls 490 are rolling members held between the shiftholder 420 and the shift base 440, and in the example illustrated inFIG. 2, three balls are used. Each of the balls 490 contacts holdingparts (not shown) formed in the shift holder 420 and the shift base 440,and are capable of rolling as the shift holder 420 moves relative to theshift base 440. The shift holder 420 is biased toward the shift base 440by a magnetic attraction member or an elastic member. Accordingly, eachof the balls 490 can be held between the shift holder 420 and the shiftbase 440 in a compressed state.

Image stabilization operations by the image sensor unit 400 having theaforementioned configuration will be described next. When the camerabody 100 is shaken due to the user's hand shaking or the like, angularshake and rotational shake arise with respect to the optical axis of theimaging optical system. As such, the image stabilization operationscancel out image shake by moving the image sensor 430 in the directionopposite from the direction in which the image shake is occurring.

When image stabilization operations are turned on using the imagestabilization setting SW 42, and hand shake has arisen in the camerabody 100 in at least one of the X direction, the Y direction, and theroll direction, the outputs of the shake detection sensor 50 in each ofthe directions are integrated, and an angular shake amount is calculatedfor each of the directions. The angular shake amount calculated for eachdirection is sent to the MPU 101.

The MPU 101 then calculates target values for controlling the movementof the image sensor 430, which is required to correct the image blur, onthe basis of the angular shake amounts from the shake detection sensor50. These target values correspond to target positions in the Xdirection, the Y direction, and the roll direction. The MPU 101calculates a shake correction amount for moving the image sensor 430 tothe position corresponding to the calculated target values, and outputsthat shake correction amount to the image stabilization driving circuit109. In accordance with the shake correction amount from the MPU 101,the image stabilization driving circuit 109 controls the electrificationof the X direction driving coil 460 a and the Y direction driving coils460 b and 460 c in order to move the image sensor 430 to the targetposition.

The position detection sensor 480 calculates a position of the mobilemember including the image sensor 430. In other words, detection signalsfor the X direction displacement, the Y direction displacement, and theroll direction rotational displacement of the image sensor 430 are sentto the MPU 101. The MPU 101 compares the target position correspondingto the target values for the X direction, the Y direction, and the rolldirection with a detected position of the image sensor 430 detected bythe position detection sensor 480. The MPU 101 outputs a control signalto the image stabilization driving circuit 109 so as to reduce adifference between the target position and the detection position. As aresult of this feedback control, the image sensor 430 moves toward thetarget position, which suppresses image blur.

Note that the image stabilization in the rotation direction (the rolldirection) may be carried out using a known technique. For example, afirst angular shake amount is calculated through a process which addsthe angular shake amount in the Y direction to the angular shake amountin the roll direction. A second angular shake amount is calculatedthrough a process which subtracts the angular shake amount in the rolldirection from the angular shake amount in the Y direction. Feedbackcontrol is carried out for the driving coil 460 b so as to eliminate adifference between the first angular shake amount obtained in thismanner and the position detected by the position detection sensor 480 b.Furthermore, feedback control is carried out for the driving coil 460 cso as to eliminate a difference between the second angular shake amountand the position detected by the position detection sensor 480 c.

Operations carried out by the camera body 100 according to the presentembodiment when image stabilization is on will be described next withreference to the flowchart in FIG. 3. First, in step S101, the MPU 101determines whether or not an operation for turning the power SW 43 onhas been made. The determination process of step S101 is repeated untilan operation for turning the power SW 43 has been made. Once the userhas made an operation for turning the power SW 43 on, and the power isturned on, the process moves to step S102.

In step S102, the MPU 101 executes a process for starting up the imagecapturing system (system on operations). Specifically, power is suppliedto the various circuits, and initial system settings, system operationsfor enabling shooting operations, and the like are carried out. Also instep S102, communication is carried out with the lens control circuit202 to obtain the lens information unique to the lens unit, i.e., theimage circle center position information, the image circle diameterinformation, the information of the highest-resolution position, and theresolution distribution information, which is recorded in the EEPROM206. The obtained information is stored in the DRAM 116.

In step S103, the MPU 101 obtains the state of the image capturingsystem, and using the lens information obtained in step S102, calculatesa position to serve as a reference during stabilization control of theimage sensor 430 (a reference position) on the basis of the obtainedstate of the image capturing system. Then, in response to a controlsignal from the MPU 101, the image stabilization driving circuit 109controls the electrification of the X direction driving coil 460 a andthe Y direction driving coils 460 b and 460 c, and moves the imagesensor 430 so that a center position of the image sensor 430 coincideswith the reference position.

The concepts of the state of the image capturing system and the movementof the center position of the image sensor 430 will be described herewith reference to FIGS. 4A, 4B, 5, and 6. The “state of the imagecapturing system” is information obtained by the MPU 101, such as thecamera orientation, the F number, the focal length, the focal state, andthe like. Here, however, only the camera orientation will be describedas an example, for the sake of simplicity.

FIGS. 4A, 5, and 6 are schematic diagrams illustrating examples of apositional relationship between the image circle of the lens unit 200and an image capturing region of the image sensor 430. The position andsize of the image circle can be obtained from the image circle centerposition information and the image circle diameter information includedin the lens information, and differ depending on the lens unit.Accordingly, the positional relationship described below is merely anexample, and differs depending on the lens unit 200.

In FIG. 4A, 300 indicates the image circle of the lens unit 200 when theorientation of the camera body 100 corresponds to the upright position.As one example, the center of an image capturing region 500 of the imagesensor 430 (i.e., the center of the image sensor 430) is assumed tocoincide with a center 300 a of the image circle 300 (i.e., the opticalaxis of the lens 201 when in the upright position).

Here, when the orientation of the camera body 100 is changed from theupright position to a vertical position rotated 90° to the right, theimage circle moves to the position indicated by 310. The image circlemoves because the lens 201 in the imaging optical system moves dependingon the camera orientation, due to manufacturing error, looseness, and soon in the lens. However, the image capturing region 500 does not move,and thus a corner part D of the image capturing region 500 will approachan outer edge part of the image circle 310. This reduces the leewayavailable for moving the image sensor 430 in order to correct imageblur. In this state, if, when viewed from the front, the image sensor430 is moved to the right in order to correct image blur, the cornerpart D will exit the image circle 310. FIG. 4B illustrates an example ofa shot image obtained when shooting a solid surface having a uniformbrightness at this time. As illustrated in FIG. 4B, a sufficient amountof light cannot be obtained at the corner part D, and thus the part ofthe shot image corresponding to the corner part D appears dark. Althoughthis problem can be solved by making the image circle larger, doing sohas the disadvantage of increasing the size of the interchangeable lensunit.

Accordingly, in the present embodiment, when the image circle moves asdescribed above in response to changes in the orientation, the imagecapturing region 500 is moved to an image capturing region 510 on thebasis of lens information based on orientation detection signals fromthe orientation detection sensor 60, as illustrated in FIG. 5. As aresult, the center of the image capturing region 510 (i.e., the centerof the image sensor 430) is caused to approach, and coincide with, acenter 310 a of the image circle 310 (i.e., the optical axis of the lens201 when in the vertical position rotated 90° to the right). Doing soprovides leeway in terms of the distance from the image capturing region510 to the outer edge part of the image circle 310 at the corner part Dof the image capturing region 510. In this state, even if, when viewedfrom the front, the image sensor 430 is moved to the right in order tocorrect image blur, the corner part D will not exit the image circle310. This makes it possible to obtain a favorable image without darknessat the corner part D of the shot image.

Although the foregoing describes causing the center of the imagecapturing region to coincide with the optical axis of the lens 201, itis not absolutely necessary to do so. The center of the image capturingregion need not coincide with the optical axis of the lens 201, as longas the image capturing region is within the range of the image circleand there is leeway in terms of the movement range of the image sensorfor the purpose of correcting image blur. For example, the center of theimage capturing region can be caused to coincide with a point, in theimage circle, having the highest resolution in a variety oforientations.

Accordingly, when information corresponding to the state of the imagecapturing system is included in the lens information obtained from thelens unit 200, that lens information can be used to reduce vignetting,improve the definition, and so on when correcting image blur.

However, the camera orientations include not only the upright positionand vertical positions, but a variety of other orientations, such as astate where the lens is pointed downward, a pitched state, anintermediate position between the upright position and a verticalposition, and so on. It is not realistic to hold lens information forall of those orientations. This is because while the lens information isobtained during the manufacturing process, it takes an extremely largenumber of steps to obtain lens information for a variety oforientations, and that number exceeds a defined number of steps.

Thus when it is determined, on the basis of the orientation detectionsignal from the orientation detection sensor 60, that the cameraorientation corresponds to a vertical position, and informationsatisfying a set condition cannot be obtained while in that orientation,the image capturing region 500 is moved to a predetermined imagecapturing region 520 in the present embodiment, as illustrated in FIG.6. Although details will be given later, in the present embodiment, aplurality of positions are prepared in advance as image capturing regionpositions, and one of those positions is selected in accordance with avariety of conditions. Not being able to obtain information satisfying aset condition, mentioned above, refers to a situation where there is nolens information for the orientation in question, a situation where itis not appropriate to estimate information corresponding to thatorientation through a method such as interpolation or extrapolation fromexisting information, or the like. This state will be called a “statenot satisfying a set condition” hereinafter, and conversely, a statewhere lens information based on that orientation can be obtained fromthe lens information will be called a “state satisfying a setcondition”.

The center of the image capturing region 520 (i.e., the center of theimage sensor 430) at this time is determined using information asidefrom the lens information obtained from the lens unit 200. For example,the center of the image capturing region 520 is caused to coincide witha center 320 of the mount part 120 of the camera body 100. Doing soprovides leeway between the outer edge part of the image circle 310 andthe image capturing region 520 at the corner part D of the imagecapturing region 520. In this state, even if, when viewed from thefront, the image sensor 430 is moved to the right in order to correctimage blur, the corner part D will not immediately exit the image circle310. The mount part 120 serves as a reference for adjusting the positionof the image sensor 430. Thus when orientation has changed, moving theimage capturing region to the image capturing region 520 produces moreleeway in the range over which the image sensor 430 can be moved for thepurpose of correcting image blur than keeping the image capturing regionat the image capturing region 500 in the upright position.

The center of the opening in the shutter unit 32 is conceivable as anexample aside from the center of the mount part 120, when there is noleeway with respect to the opening in the shutter unit 32 (the openingthrough which light beams pass from the lens 201 toward the image sensor430), for example. Additionally, when exposure control is carried outusing an electronic front curtain and rear curtain of the shutter unit32, at a high shutter speed (an exposure time of less than or equal to1/1000 sec), a position at which a curve of the electronic front curtainis adjusted is conceivable as well. In a moving image mode, the centerof a movement range defined by the driving coil 460 and the permanentmagnet 470 corresponds to the center of the image capturing region 520at which the stabilization range can be increased the most, and thus theimage capturing region is moved to that position. Using the center ofthe movement range defined by the driving coil 460 and the permanentmagnet 470 as the reference position makes it possible to set themovement range of the image sensor 430 for the purpose of correctingimage blur to a broader range. Even when not in a moving image mode, itis favorable to use the center of the movement range as the referenceposition when using settings which prioritize a stabilization function(i.e., when using settings that can handle large degrees of blur). Notethat an example of circumstances under which the center of the imagesensor 430 is moved to these positions will be described later withreference to FIG. 9.

The process for moving the center of the image sensor 430, carried outin step S103 of FIG. 3, will be described next with reference to theflowchart in FIG. 7. In step S121, the MPU 101 obtains the orientationdetection signal from the orientation detection sensor 60, as well asthe state of the image capturing system, which includes the F number,the focal length, the focal state, and so on of the lens unit 200, viathe mount contact point 21.

In step S122, it is determined whether or not the lens information inthe detected state of the image capturing system corresponds to thestate satisfying a set condition. Specifically, the lens informationloaded into the DRAM 116 in step S102 of FIG. 3 is referred to, and itis determined whether or not lens information based on the state of theimage capturing system can be obtained as appropriate. The process movesto step S123 if the state is determined to be a state satisfying a setcondition, and to step S124 if not. Note that even if the state of theimage capturing system itself cannot be obtained in step S121, theprocess nevertheless moves to step S124 under the assumption that thestate satisfying a set condition could not be obtained.

In step S123, the reference position for moving the center of the imagesensor 430 is determined in accordance with the first determinationmethod. Specifically, a position to which the center of the image sensor430 is to be moved is obtained on the basis of the lens informationobtained from the lens unit 200, as described with reference to FIG. 5.These operations will be described later in detail with reference toFIG. 8.

On the other hand, in step S124, the reference position for moving thecenter of the image sensor 430 is determined in accordance with thesecond determination method. Specifically, the reference position isdetermined using information aside from the lens information obtainedfrom the lens unit 200, as described with reference to FIG. 6. Theseoperations will be described later in detail with reference to FIG. 9.

In step S125, the center of the image sensor 430 is moved to thereference position determined in accordance with the first determinationmethod or the second determination method, after which the processreturns to FIG. 3.

FIG. 8 is a flowchart illustrating processing according to the firstdetermination method carried out in step S123 of FIG. 7. First, in stepS131, it is determined whether or not there is leeway in terms of thesize of the image circle, and whether or not the vignetting problem willarise if the image sensor 430 is subjected to stabilization driving,using the center position of the image sensor 430 while in the uprightposition as the reference position, for the purpose of correcting imageblur. In other words, if the movement range of the image sensor does notfall outside of the image circle, the process moves to step S132,whereas if even part of the movement range falls outside of the imagecircle, the process moves to step S133. In step S132, the referenceposition is set to the point where the resolution is the highest. On theother hand, in step S133, the center of the image circle is set as thereference position. The process returns to FIG. 7 after the referenceposition is set in step S132 or step S133.

FIG. 9 is a flowchart illustrating processing according to the seconddetermination method carried out in step S124 of FIG. 7. First, in stepS141, it is determined whether or not the boundary of the opening in theshutter unit 32 will produce vignetting in part of the movement range ofthe image sensor 430. If, during stabilization driving of the imagesensor 430 for the purpose of correcting image blur, the boundary of theopening in the shutter unit 32 will produce vignetting in part of themovement range of the image sensor 430, darkness may arise in part ofthe obtained image, as illustrated in FIG. 4B. Although this situationcan be avoided by broadening the boundary of the opening in the shutterunit 32, doing so is problematic in that it increases the size of thecamera as a whole. Accordingly, if the boundary of the opening in theshutter unit 32 will produce vignetting, the process moves to step S142,where the center of the opening in the shutter unit 32 is set as thereference position. If no vignetting will occur, the process moves tostep S143.

In step S143, it is determined whether or not the camera is in themoving image mode. Moving images are often shot while the photographeris moving, and are therefore likely to have a greater amount of blurthan still images. Accordingly, when the camera is in the moving imagemode, the process moves to step S144, where the center of a drive rangeused by the image stabilization mechanism unit is set as the referenceposition. Using such settings makes it possible to maximize the amountwhich the image stabilization mechanism unit can use for the purpose ofcorrecting image blur, which makes it possible to handle situationswhere there is a large amount of blur. The process moves to step S145 ifthe camera is in a still image mode.

In step S145, it is determined whether or not the shooting is using anelectronic front curtain and is being carried out at a high shutterspeed. The process moves to step S146 if the shooting is using anelectronic front curtain and is being carried out at a high shutterspeed, and to step S147 if not. Note that “high shutter speed” refers toa situation where the exposure time is shorter than a predeterminedvalue (e.g., 1/1000 sec). When shooting using an electronic frontcurtain, the front curtain is implemented through reset operations, andthus the reset position moves on the image sensor 430. On the otherhand, with the rear curtain, the rear curtain blades of the shutter unit32 move, and thus if the position of the image sensor 430 is shifted inthe travel direction of the shutter, a shift arises in the exposure aswell. The exposure time is already short at high shutter speeds inparticular (the slit width in so-called “slit travel” is narrow), andthus changes in the position of the image sensor 430 are more likely toaffect an image in such situations. This is because the amount of theshift accounts for a large proportion of the exposure time, which makesit easier for the number of exposure steps to become shifted.Accordingly, in step S146, the reference position is set to a positionat which a reset curve of the electronic front curtain (a curveindicating the timing of a front curtain curve aligned with the rearcurtain) is adjusted. This makes it possible to reduce exposure error.

On the other hand, in step S147, the center of the mount part 120 is setas the reference position. The center of the mount part 120 serves as areference for adjusting a variety of functions, and is therefore suitedto camera functions such as AF, AE, and the like in many situations. Inthe present embodiment, if the state satisfying a set condition couldnot be obtained (NO in step S122), the information used in the seconddetermination method is determined from a plurality of pieces ofinformation, in accordance with conditions of the image capturingapparatus, as illustrated in FIG. 9. However, these processes may besimplified, so that the information used in the second determinationmethod is not changed in accordance with conditions of the imagecapturing apparatus. For example, the center of the mount may always beset as the reference position if a determination of NO is made in stepS122. Additionally, in the above-described second determination method,the reference position is set on the basis of information of the imagecapturing apparatus (the center of the opening in the shutter, thecenter of operations of driving units, the position of the adjustment ofthe electronic front curtain, the center of the mount, and so on).However, the reference position may be determined in advance forsituations where the state satisfying a set condition cannot beobtained. In such a case, a position to serve as the reference positionin a situation where the state satisfying a set condition cannot beobtained (a first position) is determined in advance. Then, if adetermination of NO is made in step S122, the first position is set asthe reference position on the basis of information indicating the firstposition. In other words, if the state is one in which correspondinglens information can be obtained from the lens information stored in theEEPROM 206 (e.g., a first orientation), a determination of YES is madein step S122, and the reference position is set on the basis of thecorresponding lens information. On the other hand, if the state is onein which the corresponding lens information cannot be obtained (e.g., asecond orientation), a determination of NO is made in step S122, and thefirst position is set as the reference position.

Once the reference position is determined in the manner described above,and the center position of the image sensor 430 is moved to thedetermined reference position, the process moves to step S104 in FIG. 3.

In step S104, the MPU 101 determines whether or not the first switch SW1(41 a) of the release SW 41 has turned on. When the first switch SW1 (41a) is turned on, the process moves to step S105. However, the processreturns to step S103 if the first switch SW1 is not turned on.

In step S105, the MPU 101 carries out shooting preparation operations.The shooting preparation operations are known operations such as movingthe focus lens to an in-focus position on the basis of a focus detectionresult, calculating an exposure value by carrying out photometrycomputations, and so on, and will therefore not be described in detailhere.

In step S106, the MPU 101 determines whether or not the second switchSW2 (41 b) of the release SW 41 has turned on. When the second switchSW2 (41 b) is turned on, the process moves to step S107. However, if thesecond switch SW2 (41 b) is not operated, and the second switch SW2 (41b) is detected as being off, the process returns to step S103.

In step S107, image stabilization operations are started. Specifically,the image stabilization driving circuit 109 controls the electrificationof the X direction driving coil 460 a and the Y direction driving coils460 b and 460 c in response to control signals from the MPU 101. Theimage stabilization operations are carried out by moving the imagesensor 430 in a direction opposite from the direction of image blurcaused by hand shake or the like. Next, in step S108, the MPU 101carries out exposure control for the image sensor 430 by controlling theshutter unit 32 and the aperture stop 205 on the basis of the calculatedexposure value. Once the exposure of the image sensor 430 ends, theimage stabilization operations end in step S109. This completes theseries of shooting operations.

Note that when in the moving image mode, it is determined whether or notto start shooting a moving image in step S106, and the moving image isshot in step S108. When the moving image shooting ends, the imagestabilization operations end in step S109.

In step S110, the MPU 101 determines whether or not the power SW 43 hasbeen turned off while the image capturing system is in a standby state.If the power SW 43 has been turned off, the process moves to step S111,whereas if the power SW 43 has not been turned off, the process returnsto step S103. In step S111, the MPU 101 carries out control for endingthe operations of the various circuits in the image capturing system,storing necessary information and the like in the EEPROM 115, andcutting off the supply of power to the various circuits (operations forturning the system off).

A concept of the lens information stored in the EEPROM 206 of the lensunit 200, and the state satisfying a set condition, will be describedhere in further detail with reference to FIGS. 10A to 10C. FIGS. 10A to10C are schematic diagrams illustrating the lens information of a zoomlens having a maximum F number of 4.0 and a focal length that changesbetween 24 mm and 105 mm, for example.

FIG. 10A is a table of the lens information for a situation where theorientation of the camera corresponds to the upright position; FIG. 10Bis a table of the lens information for a situation where the orientationcorresponds to a vertical position rotated 90° to the right; and FIG.10C is a table of the lens information for a situation where theorientation corresponds to a vertical position rotated 90° to the left.In the examples illustrated in FIGS. 10A to 10C, lens informationcorresponding to three types of focal lengths (24 mm, 50 mm, and 105 mm)and four types of F numbers (F4.0, F5.6, F8.0, and F11) is present.Design values or values measured in consideration of individualdifferences are recorded in the EEPROM 206 as such lens information. Asdescribed earlier, due to the manufacturing processes, the capacity ofthe EEPROM 206, and so on, lens information such as that illustrated inFIGS. 10A to 10C is not obtained for all focal lengths, F numbers, andcamera orientations. In the examples illustrated in FIGS. 10A to 10C,the information is of only three types of orientations, three types offocal lengths, and four types of F numbers, as representative types ofinformation. Each instance of the lens information (PN11 to PN43, PR11to PR43, and PL11 to PL43) includes the image circle center positioninformation, the image circle diameter information, the information ofthe highest-resolution position, the resolution distributioninformation, and the like, as described above.

Here, if, for example, the upright position, a focal length of 50 mm,and an F number of 4.0 has been obtained as the state of the imagecapturing system, information indicated by PN12 is obtained from theupright position table illustrated in FIG. 10A.

Additionally, assume that, for example, the upright position, a focallength of 35 mm, and an F number of 4.0 have been obtained as the stateof the image capturing system. In this case, it is thought that asufficiently good approximation can be obtained by interpolating theinformation of PN11, i.e., the upright position, a focal length of 24mm, and an F number of 4.0, and the information of PN12, i.e., theupright position, a focal length of 50 mm, and an F number of 4.0, fromthe table for the upright position illustrated in FIG. 10A. Accordingly,when the state of the image capturing system matches a state held in thelens information illustrated in FIGS. 10A to 10C, and the state can beapproximated, that state is taken as the state satisfying a setcondition. When the state satisfies a set condition in this manner (YESin step S122 of FIG. 7), the reference position is determined throughthe first determination method (step S123).

On the other hand, if, for example, the orientation is one in which thelens is pointing downward, a suitable reference position cannot be foundthrough interpolation using the lens information for the uprightposition, the vertical position rotated 90° to the right, and thevertical position rotated 90° to the left, as illustrated in FIGS. 10Ato 10C.

Furthermore, in the image capturing system according to the presentembodiment, the lens unit 200 can be attached to and removed from thecamera body 100. With such an image capturing system, it is conceivable,in addition to the aforementioned manufacturing process, EEPROM 206capacity, and so on, that another lens unit which the user possessesdoes not have the lens information.

Such a state corresponds to a case where the set condition is notsatisfied, and lens information according to the image capturing systemcannot be obtained. In this case, (NO in step S122 of FIG. 7), thereference position is determined through the second determination method(step S124). Note that when a lens unit not having lens information isattached to the camera body 100, the corresponding lens informationcannot be obtained no matter what orientation the camera is in, and thusthe reference position is determined through the second determinationmethod regardless of the orientation. In other words, in the presentembodiment, there are cases where, depending on the attached lens unit,the state satisfying a set condition can or cannot be obtained, evenwhen the orientation is the same (e.g., the upright position).Therefore, the reference position may be determined using the firstdetermination method on one occasion and the reference position may bedetermined using the second determination method on another occasioneven when the orientation is the same.

The timing at which the center of the image sensor 430 is moved when thestate of the image capturing system has changed will be described nextwith reference to FIG. 3.

First, in step S103, the reference position is found, and the center ofthe image sensor 430 is moved, on the basis of the state of the imagecapturing system at the point in time when the power SW 43 is turned on.A captured subject image is then displayed in the screen of the colorliquid crystal monitor 19 (a through-the-lens image display). Toconserve power, if it is determined, on the basis of an output signalfrom the proximity sensor 70, that the user is looking through theviewfinder 33, the image is displayed in the screen of theeyepiece-based liquid crystal monitor 30 instead of the color liquidcrystal monitor 19. The monitor display is carried out after firstmoving the center of the image sensor 430 to the target position, andthus the user will not notice the movement of the image sensor 430. Inother words, the user will not notice any fluctuations in the angle ofview, which has the advantage of allowing him or her to concentrate ontaking the shot.

Then, if the state of the image capturing system has changed without theuser turning SW1 on, the process returns to step S103, where thereference position is found again in accordance with the timing ofchange in the state of the image capturing system. The center of theimage sensor 430 is then moved. The timing at which the state of theimage capturing system has changed can be determined by the MPU 101 froman output signal from the shake detection sensor 50, an output signalfrom the orientation detection sensor 60, and through communication withthe lens control circuit 202. Generally speaking, there is a littledemerit to the user even if the center of the image sensor 430 is moved,and the angle of view changes as a result, in response to a change inthe state of the image capturing system prior to the first switch SW1(41 a) turning on.

According to the present embodiment as described thus far, imagestabilization in which the influence of vignetting is suppressed can becarried out in accordance with a variety of states in the imagecapturing system.

Second Embodiment

A second embodiment of the present invention will be described next withreference to FIG. 11. In the second embodiment, the timing at which thecenter of the image sensor 430 moves is different from that in theprocess illustrated in FIG. 3. Aside from this, the configuration of andprocessing carried out by the image capturing system is the same as inthe first embodiment. Descriptions thereof will accordingly be omitted,and the following will focus only on the differences.

According to the second embodiment, in a state where the first switchSW1 (41 a) is off, the center of the image sensor 430 is not moved evenif the user makes various changes to the state of the image capturingsystem. Instead, the center of the image sensor 430 is moved after thefirst switch SW1 (41 a) has turned on. FIG. 11 is a flowchartillustrating that process, and differs from the process illustrated inFIG. 3 in that the process for moving the center of the image sensor430, carried out in step S103, is carried out in accordance with thestate of the image capturing system at the point in time when the firstswitch SW1 (41 a) has turned on in step S104. In other respects, theprocess is the same as that illustrated in FIG. 3, and will thereforenot be described here.

Carrying out such control makes it possible to achieve the followingeffects, in addition to the effects described above in the firstembodiment. First, in a state where the first switch SW1 (41 a) is noton, the image sensor 430 need not be moved each time the state of theimage capturing system changes. This makes it possible to keep theelectrification of the driving coils to a minimum, which in turn reducesthe amount of power consumed. This control is also useful for users whofind it annoying when the angle of view changes each time the state ofthe image capturing system changes while the first switch SW1 (41 a) isoff. Furthermore, the movement of the center of the image sensor 430 inaccordance with the state of the image capturing system need only becarried out once after the first switch SW1 (41 a) has turned on.

On the other hand, the user is focusing on the image displayed in thecolor liquid crystal monitor 19 or the eyepiece-based liquid crystalmonitor 30 after the first switch SW1 (41 a) has turned on. The imagesensor 430 is moved at that time, which means that the user may noticethe angle of view fluctuating. However, by noticing fluctuations in theangle of view, the user can change the angle of view and recompose theshot before proceeding to turn the second switch SW2 (41 b) on, whichmakes it possible to suppress the effect of the fluctuation in the angleof view on the shot image.

In the example illustrated in FIG. 11, the process for finding thereference position in step S103 and the process of moving the center ofthe image sensor 430 are carried out after the first switch SW1 (41 a)turns on, but the present invention is not limited thereto. For example,control may be carried out so that the process for finding the referenceposition is carried out as needed before the first switch SW1 (41 a)turns on, and after the first switch SW1 (41 a) has turned on, thecenter of the image sensor 430 is moved to the reference position foundimmediately before.

Third Embodiment

A third embodiment according to the present invention will be describednext. In the first embodiment, the center of a range of driving by theimage stabilization mechanism unit is used as the reference positionwhen the shooting mode is the moving image mode in the seconddetermination method (YES in step S143), as illustrated in FIG. 9. Asopposed to this, in a third embodiment, the center of the image sensor430 is moved when the moving image mode is set. Aside from this, theconfiguration of and processing carried out by the image capturingsystem is the same as in the first embodiment. Descriptions thereof willaccordingly be omitted, and the following will focus only on thedifferences.

FIG. 12 is a flowchart illustrating operations carried out by the camerabody according to the third embodiment. Note that processes that are thesame as those illustrated in FIG. 3 are given the same step numbers, anddescriptions thereof will be omitted as appropriate.

In step S401, the MPU 101 determines whether or not the shooting modesetting dial 44 is set to the moving image mode. The process moves tostep S103 if the moving image mode is set. In step S103, on the basis ofthe state of the image capturing system, the MPU 101 moves the imagesensor 430 so that the center of the image sensor 430 coincides with thereference position, as described earlier with reference to FIGS. 7 to 9.Note that if the reference position is found through the seconddetermination method, the determination in step S143 of FIG. 9 willalways be YES, and thus the processing from step S145 to S147 is notcarried out.

Note that as described above, moving images are more likely to have agreater amount of blur than still images, and thus when the moving imagemode is set, the center of the range of driving by the imagestabilization mechanism unit may always be set as the referenceposition, regardless of the lens information.

Then, in step S402, the MPU 101 controls the shooting preparationoperations according to the moving image mode. In step S403, the MPU 101determines whether or not moving image shooting has been started. Thesecond switch SW2 (41 b) of the release SW 41 being turned on is usedhere as an operation for starting moving image shooting. Of course, thepresent invention is not limited thereto. A separate moving imageshooting switch may be provided, and whether moving image shooting hasstarted or ended may be determined in response to the moving imageshooting switch being operated. Aside from a moving image being shot instep S108, the processing from steps S107 to S111 is the same as thatdescribed with reference to FIG. 3.

Note that if the mode is determined not to be the moving image mode instep S401, the processing illustrated in FIG. 3 or FIG. 11 may becarried out.

By carrying out such control, the center of the image sensor 430 ismoved at the timing at which the mode is changed from the still imagemode to the moving image mode. This makes it possible to suppress theeffects of fluctuations in the angle of view.

Note that even if the state of the image capturing system has beenchanged while a moving image is being shot in step S108 (e.g., the statehas been changed from the upright position to a vertical position), thereference position is not changed. The change is instead made when thestart of moving image shooting is determined in step S103. This isbecause if the center of the image sensor 430 is moved while shooting amoving image, the angle of view of the shot image will change suddenly,producing a sense of discontinuity in the moving image. Such a sense ofdiscontinuity in the moving image greatly reduces the moving imagequality, and thus the center of the image sensor 430 is not moved evenif the state of the image capturing system has changed.

In this manner, control is carried out so that the image sensor is notmoved if a fluctuation in the angle of view caused by the image sensormovement will greatly reduce the quality of the shot image. This makesit possible to carry out image stabilization which suppresses theeffects of vignetting.

Fourth Embodiment

A fourth embodiment of the present invention will be described next. Inthe fourth embodiment, control is carried out so that the center of theimage sensor 430 is not moved if the state of the image capturing systemchanges while the user is looking through the viewfinder 33. The processfor moving the center of the image sensor 430 carried out at this time,indicated by step S103 in FIG. 3, will be described in detail withreference to the flowchart in FIG. 13. Note that this process is carriedout instead of the process illustrated in FIG. 7, and thus processingthat is the same as that in FIG. 7 will be described using the samereference signs. Aside from this, the configuration of and processingcarried out by the image capturing system is the same as in the firstembodiment. Descriptions thereof will accordingly be omitted, and thefollowing will focus only on the differences.

First, in step S121, the state of the image capturing system, i.e., thecamera orientation, the F number, the focal length, the focal state, andso on, is obtained. Next, in step S501, the MPU 101 determines whetheror not the user is looking through the viewfinder 33 of the camera body100 (i.e., has his or her eye close to the viewfinder 33) on the basisof an output signal from the proximity sensor 70. The process ends if itis determined that the user is looking through the viewfinder 33. Inother words, the center of the image sensor 430 is not moved. However,the process moves to step S122 if it is determined that the user is notlooking through the viewfinder 33.

In step S122, the MPU 101 determines whether or not the state of theimage capturing system, obtained in step S121, satisfies theaforementioned set condition. If the set condition is satisfied, in stepS123, a target position in the center of the image capturing region isdetermined in accordance with the first determination method. However,if the set condition is not satisfied, in step S124, a target positionin the center of the image capturing region is determined in accordancewith the second determination method.

In step S125, the center of the image sensor 430 is moved to theposition determined in accordance with the first determination method orthe second determination method, after which the process returns to FIG.3.

If the user changes the camera orientation while observing a subjectimage through the viewfinder 33, it is conceivable that he or she willnotice an unanticipated fluctuation in the angle of view, and willtherefore be unable to concentrate on taking the shot. Additionally, ifthe camera orientation has been changed during a composition which hasthe subject image within the center of the screen of the eyepiece-basedliquid crystal monitor 30, a fluctuation in the angle of view may causethe subject image to shift from the center of the screen, confusing theuser. Accordingly, carrying out control such as that illustrated in FIG.13 ensures that the center of the image sensor 430 will not move even ifthe camera orientation is changed while the user is looking through theviewfinder 33. This makes it possible to solve the aforementionedproblem. Unanticipated fluctuations in the angle of view while theuser's eye is close to the viewfinder negatively impacts the user'schance to take a shot, and thus carrying out such control makes itpossible to suppress occurrences of failed shooting.

According to the control carried out in the fourth embodiment asdescribed above, the image sensor is not moved at timings wherefluctuations in the angle of view caused by image sensor movement maynegatively impact the user's chance to take a shot. By carrying out suchcontrol, image stabilization which suppresses the effects of vignettingcan be carried out within a range that does not interfere with theuser's chance to take a shot.

Note that the present invention may be applied both in a systemconstituted by a plurality of devices, and in an apparatus constitutedby a single device.

OTHER EMBODIMENTS

Embodiment(s) of the present invention can also be realized by acomputer of a system or apparatus that reads out and executes computerexecutable instructions (e.g., one or more programs) recorded on astorage medium (which may also be referred to more fully as a‘non-transitory computer-readable storage medium’) to perform thefunctions of one or more of the above-described embodiment(s) and/orthat includes one or more circuits (e.g., application specificintegrated circuit (ASIC)) for performing the functions of one or moreof the above-described embodiment(s), and by a method performed by thecomputer of the system or apparatus by, for example, reading out andexecuting the computer executable instructions from the storage mediumto perform the functions of one or more of the above-describedembodiment(s) and/or controlling the one or more circuits to perform thefunctions of one or more of the above-described embodiment(s). Thecomputer may comprise one or more processors (e.g., central processingunit (CPU), micro processing unit (MPU)) and may include a network ofseparate computers or separate processors to read out and execute thecomputer executable instructions. The computer executable instructionsmay be provided to the computer, for example, from a network or thestorage medium. The storage medium may include, for example, one or moreof a hard disk, a random-access memory (RAM), a read only memory (ROM),a storage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2019-088574, filed on May 8, 2019 which is hereby incorporated byreference herein in its entirety.

1. An image stabilization apparatus, comprising at least one processorand/or circuitry which function as: a first obtaining unit that obtains,from at least one of an image capturing apparatus and a lens unitattached to the image capturing apparatus, a state of the imagecapturing apparatus and/or the lens unit; a determining unit thatdetermines a reference position of an image sensor included in the imagecapturing apparatus; and a calculating unit that calculates a correctionamount for performing image stabilization by moving a position of theimage sensor from the reference position in a plane intersecting with anoptical axis, wherein a method of determining the reference position bythe determination unit differs between a case where the state satisfyinga predetermined condition is obtained by the first obtaining unit and acase where the state satisfying the predetermined condition is notobtained by the first obtaining unit.
 2. The image stabilizationapparatus according to claim 1, wherein the at least one processorand/or circuitry further function as: a second obtaining unit that, in acase where the state satisfies the predetermined condition, obtains lensinformation corresponding to the state from lens information of the lensunit corresponding to a plurality of predetermined states; wherein in acase where the state satisfying the predetermined condition is obtainedby the first obtaining unit, the determining unit determines thereference position through a first method based on lens informationcorresponding to the state obtained by the second obtaining unit.
 3. Theimage stabilization apparatus according to claim 2, wherein the lensinformation includes at least one of image circle center positioninformation, image circle diameter information, and information of ahighest-resolution position of the lens unit.
 4. The image stabilizationapparatus according to claim 1, wherein in a case where the statesatisfying the predetermined condition is not obtained by the firstobtaining unit, the determining unit determines the reference positionthrough a second method based on information aside from the lensinformation.
 5. The image stabilization apparatus according to claim 4,wherein the information aside from the lens information is informationindicating a predetermined first position; and the second method is amethod that sets the first position as the reference position.
 6. Theimage stabilization apparatus according to claim 5, wherein thedetermining unit: sets a different reference position in accordance withthe state in a case where the state satisfying the predeterminedcondition has been obtained by the first obtaining unit; and sets thefirst position as the reference position in a case where the statesatisfying the predetermined condition has not been obtained by thefirst obtaining unit.
 7. The image stabilization apparatus according toclaim 4, wherein information aside from the lens information is theinformation of the image capturing apparatus.
 8. The image stabilizationapparatus according to claim 2, wherein in a case where the statesatisfying the predetermined condition is not obtained by the firstobtaining unit, the determining unit determines the reference positionthrough a second method based on information aside from the lensinformation.
 9. The image stabilization apparatus according to claim 8,wherein the information aside from the lens information is informationindicating a predetermined first position; and the second method is amethod that sets the first position as the reference position.
 10. Theimage stabilization apparatus according to claim 8, wherein informationaside from the lens information is the information of the imagecapturing apparatus.
 11. The image stabilization apparatus according toclaim 1, wherein the image capturing apparatus includes an actuator thatmoves the image sensor; and the image sensor is moved to the referenceposition by the actuator before shooting preparations have beeninstructed by the image capturing apparatus.
 12. The image stabilizationapparatus according to claim 1, wherein the image capturing apparatusincludes an actuator that moves the image sensor; and the image sensoris moved to the reference position by the actuator after shootingpreparations have been instructed by the image capturing apparatus. 13.The image stabilization apparatus according to claim 1, wherein theimage capturing apparatus includes a viewfinder and at least oneprocessor and/or circuitry which function as a detecting unit thatdetects in a case where a user is close to the viewfinder; and the imagesensor is controlled not to move to the reference position in a casewhere the detecting unit has detected that the user is close to theviewfinder.
 14. The image stabilization apparatus according to claim 1,wherein the predetermined condition is that lens information accordingto the state obtained by the first obtaining unit can be obtained on thebasis of the lens information corresponding to the plurality of states.15. The image stabilization apparatus according to claim 1, wherein theimage capturing apparatus includes a viewfinder and at least oneprocessor and/or circuitry which function as a detecting unit thatdetects in a case where a user is close to the viewfinder; and the imagesensor is controlled not to move to the reference position in a casewhere the detecting unit has detected that the user is close to theviewfinder.
 16. The image stabilization apparatus according to claim 1,wherein the state of the image capturing apparatus includes theorientation of an image capturing apparatus.
 17. The image stabilizationapparatus according to claim 1 further comprising the image sensor. 18.An image stabilization control method, comprising: obtaining, from atleast one of an image capturing apparatus and a lens unit attached tothe image capturing apparatus, a state of the image capturing apparatusand/or the lens unit; determining a reference position of an imagesensor included in the image capturing apparatus; and calculating acorrection amount for performing image stabilization by moving aposition of the image sensor from the reference position in a planeintersecting with an optical axis, wherein a method of determining thereference position differs between a case where the state satisfying apredetermined condition is obtained and a case where the statesatisfying the predetermined condition is not obtained.
 19. Anon-transitory computer-readable storage medium in which is stored aprogram for causing a computer to function as the respective units inthe image stabilization apparatus comprising: a first obtaining unitthat obtains, from at least one of an image capturing apparatus and alens unit attached to the image capturing apparatus, a state of theimage capturing apparatus and/or the lens unit; a determining unit thatdetermines a reference position of an image sensor included in the imagecapturing apparatus; and a calculating unit that calculates a correctionamount for performing image stabilization by moving a position of theimage sensor from the reference position in a plane intersecting with anoptical axis, wherein a method of determining the reference position bythe determination unit differs between a case where the state satisfyinga predetermined condition is obtained by the first obtaining unit and acase where the state satisfying the predetermined condition is notobtained by the first obtaining unit.